Similar situation.... 5Dii and 7D
Social events can be tricky. The 24-70 you have should do ok for small gatherings, and you can mount the 50/1.4 on the 7D for the occaional need to shoot a head n shoulders shot. Most events are not head and shoulder shots though.
In a few weeks I'll be shooting at Biketoberfest, downtown Main Street Daytona. Gonna use the 16-35 on the 5Dii and 20/2.9 on the 7D as backup. The 5Dii will have the big flash rig, while I'll just rely on the 7D little internal flash for the occaional time I'll need it. The 20mm lens is like my favorite 35mm in coverage on FF, so alls well there. Keep in mind that Biketoberfest is a ZOO and the 16-35 will be getting its workout.
For a wedding... not sorry to say, I'd shoot a wedding with the following: 35mm lens on the FF, and 50mm lens on the crop, so I'd probably use the 16-36 at the 35 end all the time, backing off maybe if I had a really big group to shoot in a really tight space. I prefer to shoot groups with the 35 lens... they look more natural, but often space is a consideration.
You need a 16-35